Question: I've lost some of my upgrades after completing some missions and then checking my garage. What should I do?
Answer: We have received some reports about problems with cars and garages, particularly after upgrading and then completing a mission, and are looking into this now. Unfortunately, we do not currently have a workaround to recover a car if it is missing. If you would like to receive an automatic email notification as soon as there is more information, please log into the Support Site and click Subscribe at the top of this page.
Also please note that vehicles saves in the garage of one safehouse (Franklin's Aunt's) may not show up in the garage of a different safehouse (Franklin's Vinewood Hills).
Updated 10/8/13: This issue was resolved through a Title Update. To make sure you have the latest update, boot the game while connected to Xbox Live or PlayStation Network. If you do not have the latest update, a download prompt will appear as soon as the game starts. To browse the full list of changes from all past GTAV Title Updates, please go to: http://support.rockstargames.com/hc/en-us/sections/200102328-Grand-Theft-Auto-V-Title-Update-Information